The field of the invention is electrical junction boxes and conduit junction boxes. Conduit junction boxes are a type of electrical junction box. Most building codes require most electrical wiring to be enclosed in conduits which are coupled to one another at junction boxes. A typical junction box has a hollow body with at least one open side. A junction box may have threaded or non-threaded coupling hubs extending through the walls of the box and an interior space that is accessible through an open side of the box. The coupling hubs provide the point of connection between the conduit and the junction box. Electric conductors or wires extend through the conduit into the junction boxes where they are commonly spliced or joined. The open side of a junction box is then closed with a removable cover that is usually attached to the body of the junction box with screws or other fasteners. Examples of prior electrical conduit systems and junction boxes are described in U.S. Pat. Nos. 1,741,358; 2,208,558; 2,398,782; 4,936,478; and my U.S. Reissue Pat. No. RE 35,075.
A common shape for a conduit box is one with a generally rectangular or oblong body, one open longitudinal side, curved ends, and coupling hubs at one or more various locations on the body. The oblong shape increases the ease of routing and pulling wire through the conduit and into the junction box, and the elimination of sharp or jagged edges prevents damage to the wire's insulation by preventing snagging. Conduit bodies are assigned various series or type designations (such as LL, LB, LR, T, X, E, and C) which specify the number and locations of these coupling hubs. These specifications which also include dimensions, interior volume, and maximum numbers of conductors as are more fully set forth in Article 370 of the National Electrical Code (NEC) Hand Book, Twenty-Fourth Edition, published by the National Fire Protection Association which is incorporated herein by reference.
Other configurations of conduit boxes not specified by the NEC Hand Book are in use. Boxes in use include those having a configuration which is square, cylindrical, hexagonal and so on. While the present invention describes an adapter cover and assembly directed to the Hand Book configuration, it is contemplated that the present invention is readily adaptable to these other shapes of boxes and is not limited to the NEC shapes alone.
Conduit bodies form a special subset of conduit systems. The inside of a conduit body is accessed through the removable cover. Large cast or sheet metal boxes are not classified as conduit bodies. Conduit bodies cannot be concealed or buried underground. Under the National Electrical Code, they must be either above ground or, if underground, must be accessible at all times. They can be installed indoors or outdoors and in damp locations, are dust proof and are coated inside and out to prevent corrosion.
A conduit body's coupling hubs provide the connection interfaces with the conduit. Coupling hubs are a fixed feature on the conduit body. Because the location and orientation of the coupling hubs are fixed, the modification of or addition of more conduits to an in-service conduit body can only be achieved by removing and replacing the conduit body with one possessing a more favorable coupling hub configuration. Removing and replacing the conduit body would require undoing all of the wiring connections and rewiring the connections inside the new conduit body, which is a costly and time-consuming operation. The other option is to add an extension box, which would not require removal and rewiring the in-service conduit body. This is the substance of my U.S. Pat. No. Re 35,075. However, this is may not always be the most efficient or economical means if for example, one is adding only one new conduit to an existing system because an extension box also contains a large interior space and usually multiple coupling hubs; hence unnecessary additional structure would be involved. An example of the use of extension boxes may be seen in my U.S. Pat. No. RE 35,075. A much more efficient, cost-effective, and streamlined result is achieved by the present invention; and that is particularly the case where my extension box has been employed as the in-service junction box, as my previous patent suggests as an alternative use thereof. Other variations of the present invention provide other alternatives.